The present invention relates to an improvement in a control valve.
Generally, in the field of the power steering mechanism for vehicles, it is known to provide a control valve which controls oil feed and exhaust from an oil source to a power rotatably inserted in the valve sleeve and connected with a steering wheel shaft and having a plurality of fluid passages opposing with the fluid passages of the valve sleeve. The fluid passage of the valve sleeve is formed by a through passage which passes through the wall of the valve sleeve and a recessed groove formed on the inner surface of the sleeve. In such conventional control valve, by rotating the rotor the fluid passages of the rotor cooperate with the fluid passages of the valve sleeve to flow fluid from the fluid passages of the valve sleeve to the fluid passages of the rotor and to shut off fluid flow. However, in such known art, rather heavy fluid flow noise is generated between the fluid passages of the rotor and the recessed grooves forming a portion of the fluid passages of the valve sleeve when the fluid passages of the rotor is just aligned or just out of alignment with the fluid passages of the valve sleeve.
Conventional attempt to solve the problem and to reduce the fluid flow noise is to divide the fluid passage to reduce flow rate per one fluid passage. However, such attempt decreases total flow rate in the valve to decrease valve efficiency, and manufacturing cost of the valve also increases.